Conceptual design and analysis of a two-stage underwater glider for ultra-long voyage

An underwater glider (UG) designed for ultra-long voyage undoubtedly requires additional battery energy, which is generally realized by increasing the volume. However, a larger volume of UG results in a larger net buoyancy loss caused by seawater density variation and hull deformation, which will lead to a larger energy consumption. This study proposes the conceptual design of a novel two-stage UG (TUG) for enhancing the voyage range. To reduce the volume of UG, the first stage will be separated from the glider and discarded after its battery energy is drained. Mathematical models for the TUG are established, including the dynamic model, the energy con-sumption model and the performance evaluation models. To better evaluate this novel design, a multi-objective optimization model considering the energy utilization rate and voyage velocity is developed based on the pro-posed models, and implemented by surrogate model and non-dominated sorting genetic algorithm II. The results demonstrate that the designed TUG has a better motion performance than conventional UGs, and the two-stage design is more suitable for UGs with low hotel loads, which can theoretically improve the voyage range by 16.6% at a 0.25 W hotel load. This work can provide theoretical guidance for the optimization design of UGs applied for ultra-long voyage.